U8RARY 
OF  THE 

WHV0WIY  OF  UMM 


HARVARD  COLLEGE 


CHEMISTRY  1 

. 

INORGANIC  CHEMICAL  PREPARATIONS 


L.  CLARKE 


1908 


CHEMISTRY  1 


INORGANIC  PREPARATION  II. 


\ 


Pure  Sodium  Chloride. 


Common  salt  contains  impurities  of  sulphates,  the  alkaline  earths, 
and  the  so-called  heavy  metals.  These  can  be  eliminated  by  the 
following  procedure : — 

Dissolve  100  grams  common  salt  in  350  cc.  water  in  an  evapo- 
rating dish.  In  a beaker,  slake  about  two  grams  of  lime  and  add 
sufficient  water  to  make  a thin  paste,  which  is  known  as  “ milk  of 
lime,”  add  this  to  the  hot  salt  solution,  stir  thoroughly  and  filter. 
Treat  the  hot  filtrate  with  barium  chloride  until  all  sulphate  is  pre- 
cipitated, then  add  pure  sodium  carbonate  solution  in  slight  excess, 
which  will  throw  down  the  alkaline  earths.  Filter,  and  add  pure 
hydrochloric  acid  till  neutral.  Evaporate  to  crystallization.  Dry 
the  crystals  in  the  air  bath. 

Write  the  reactions  involved  in  this  purification,  and  look  up  the 
properties  of  sodium  chloride  in  your  lecture  note-book. 

The  pure  salt  should  give  a perfectly  clear  solution,  and  should 
give  a precipitate  neither  with  barium  chloride  nor  sodium  carbonate. 


INORGANIC  PREPARATION  III. 


t 


Potassium  Perchlorate. 


In  an  evaporating  dish  heat  gently  50  grams  of  potassic  chlorate, 
until,  after  having  melted,  it  becomes  thick  and  pasty.  After  cool- 
ing, break  up  the  mass  and  extract  twice  with  2000  cubic  centimetres 
of  cold  water  to  remove  potassic  chloride ; then  recrystallize  from 
hot  water  in  the  following  manner : dissolve  the  perchlorate  in  the 
smallest  possible  amount  of  hot  water,  set  aside  to  cool,  and  when 
perfectly  cold  filter  with  the  Buchner  funnel  and  wash  the  crystals 


738826 


2 


with  a few  cubic  centimetres  of  cold  water.  Dry  the  crystals  by 
exposure  to  the  air  on  filter  paper  for  a few  hours,  and  transfer  to  a 
dry  bottle. 

Reaction,  (a)  4 KC103=r  KC1+3  KC104. 

(6)  8 KC103  = 5 KC104  + 3 KCl  + 202. 

Potassic  perchlorate  is  soluble  0.7  parts  in  100  of  water  at  0°; 
and  20  parts  in  100  of  water  at  100°. 

INORGANIC  PREPARATION  IV. 

s 

Calcic  Chloride  (crystals)  CaCl2  6H20. 

In  an  evaporating  dish  put  100  grams  of  marble  and  neutralize 
with  hydrochloric  acid  (Sp.  Gr.  1.2)  by  adding  the  acid  in  small 
portions  at  a time,  stirring  thoroughly  and  allowing  the  effervescence 
practically  to  stop  before  adding  more  acid.  When  the  marble  is 
all  dissolved,  add  enough  milk  of  lime  to  make  the  solution  slightly 
alkaline.  Add  a few  cubic  centfmeters  of  chlorine  water  and  boil 
ten  or  fifteen  minutes,  then  make  strongly  alkaline  with  milk  qf  lime, 
and  boil,  until  a test  portion  gives  no  test  for  iron.  (The  test  for 
iron  is  potassium  ferrocyanide,  K4Fe(CN)6,  which  gives  a blue  pre- 
cipitate in  acid  solution.  Try  this  with  some  ferric  chloride.)  Filter 
hot,  and  evaporate  the  filtrate  over  the  free  flame  until  a crust  begins 
to  form  around  the  edge,  then  set  aside  to  cool  slowly. 

The  crystals  of  calcic  chloride  are  very  deliquescent  and  so  should 
not  be  exposed  to  the  air.  For  a sample,  two  or  three  good  crystals 
may  be  removed  from  the  mother  liquor,  dried  with  filter  paper 
hurriedly,  and  placed  in  a dessicator  over  concentrated  sulphuric 
acid  a few  days,  then  preserved  in  a dry,  cold,  bottle  with  well- 
fitting greased  stopper. 

The  mother  liquor  and  remaining  crystals  can  be  used  for  the  next 
preparation. 

Calcic  chloride  prepared  in  this  way  should  give  a clear,  neutral 
solution  in  water.  This  solution  should  not  be  affected  either  by 
hydrogen  sulphide  or  by  ammonium  sulphide.  These  reagents  detect 
the  presence  of  the  “ heavy  metals/’. iron,  for  example.  The  aqueous 
solution  of  calcic  chloride  should  not  give  off  traces  of  ammonia  when 
heated  with  sodic  or  potassic  hydrate. 


f 


3 


INORGANIC  PREPARATION  V. 

\ 

Calcic  Carbonate.  CaC03. 

Add  sufficient  water  to  the  crystals  of  calcic  chloride  obtained 
in  the  last  preparation,  to  make  a complete  solution,  and  heat  nearly 
to  boiling  (about  95°).  Add  a strong  filtered  solution  of  ammonic 
— carbonate  to  complete  precipitation.  Allow  the  precipitate  to  settle, 
and  pour  off  the  supernatant  liquor  through  a Buchner  funnel,  finally 
transferring  the  precipitate  also  to  the  filter,  and  remove  the  mother 
liquor  thoroughly  by  suction.  Wash  the  precipitate  with  hot  water 
till  the  last  portion  of  the  filtrate  is  free  from  chlorides,  and  dry  on 
filter  paper  over  the  hot  plate.  Bottle  the  ptoduct  in  a weighed 
bottle  and  calculate  the  yield  from  the  original  marble,  making  allow- 
ance for  the  crystals  of  the  crystallized  calcic  chloride  retained  as 
a sample.  % 

Pure  calcic  carbonate  made  in  this  way  dissolves  in  pui\e  dilute 
hydrochloric  acid,  giving  a clear  solution,  which  should  not  contain 
iron,  aluminium,  magnesium,  or  appreciable  sulphates. 

Iron  may  be  detected  by  potassium  ferrocyanide,  K4Fe(CN)6. 
To  learn  the  tests  for  aluminium  and  magnesium  perform  the  follow- 
ing test-tube  experiments : — 

(1)  To  aluminic  sulphate  solution  add  ammonic  hydrate. 

(2)  To  magnesic  sulphate  solution  add  ammonic  chloride,  ammonic  • 
hydrate,  and  sodic  phosphate. 

INORGANIC  PREPARATION  VI. 

Baric  Chloride.  BaCl2  2H20. 

Weigh  out  100  grams  of  barite,  or  precipitated  baric  sulphate 
will  do,  and  add  15  grams  of  powdered  charcoal.  Mix  very  thoroughly 
and  transfer  to  a clay  crucible  with  a cover.  Heat  the  mixture  in 
the  furnace  for  about  an  hour  and  a half,  then  allow  to  cool.  Extract 
the  crucible  contents  two  or  three  times  with  hot  water,  filter  into  a 
flask,  fit  this  with  funnel  and  delivery  tubes,  and  add  hydrochloric 
acid  to  slight  excess.  Since  a large  amount  of  hydrogen  sulphide 
is  evolved  this  must  be  done  under  the  hood,  and  the  hydrogen  sul- 


4 


pliide  absorbed  by  caustic  soda  solution.  The  tube  leading  into  the 
flask  containing  the  caustic  should  not  dip  below  the  surface  of  the 
liquid  but  should  remain  about  an  eighth  of  an  inch  above  it.  Filter 
the  solution  of  baric  chloride  so  obtained  and  evaporate  to  dryness ; 
redissolve  in  hot  water,  filter  hot  (plaited  filter),  and  evaporate  to 
crystallization.  Filter  with  the  Buchner  funnel.  Recrystallize  from 
distilled  water,  filter  again  by  suction  and  dry  the  crystals  in  the  des- 
sicator.  Weigh  and  calculate  the  per  cent,  of  yield  of  baric  chloride 
from  the  given  amount  of  baric  sulphate. 

Reactions  for  the  process  : — 

BaS04  + 4C  = BaS  + 4CO 
BaS  + 2HC1  = BaCl2  + H2S. 

Read  up  the  account  of  baric  chloride  in  your  lecture  notes. 


INORGANIC  PREPARATION  VII. 
v Zinc  Carbonate  ZnC03. 

Dissolve  50  grams  of  zinc  sulphate  in  50  grams  of  boiling  water 
and  pour  slowly  with  stirring  into  a boiling  solution  of  40  grams  of 
sodium  bicarbonate  in  200  cubic  centimetres  of  water.  Allow  the 
precipitate  to  settle  and  wash  by  decantation  with  boiling  water  until 
the  washings  are  free  from  sulphate.  Filter  on  cloth  and  dry  in  the 
air  bath. 

This  procedure  gives  essentially  pure  ZnC03.  If  normal  sodium 
carbonate  were  used  the  precipitate  would  be  a basic  salt  of  indefinite 
composition.  If  the  sodium  bicarbonate  were  added  to  the  zinc  sul- 
phate, a basic  carbonate  of  zinc  would  be  produced,  which  further 
quantities  of  NaHC03  would  decompose  only  with  much  difficulty. 
It  is  necessary  to  have  always  present  an  excess  of  NaHC03. 

Zinc  carbonate  is  a pure  white  powder.  Try  its  solubility  in 
water,  NaOH  and  HC1. 


5 


INORGANIC  PREPARATION  VIII. 

V 

Aluminic  Chloride  AlCl3. 

( Anhydrous . ) 

Dry  aluminic  chloride  cannot  be  obtained  pure  by  a wet  method, 
so  the  following  special  procedure  has  to  be  employed  in  its  prep- 
aration. 

Fit  a 500  cubic  centimetre  flask  with  a 2 hole  rubber  stopper; 
through  one  hole  of  the  stopper  pass  a funnel  tube  reaching  nearly 
to  the  bottom  of  the  flask,  and  through  the  other,  a delivery  tube 
bent  at  a right  angle  and  connecting  with  two  special  wash  bottles. 
(See  diagram  posted  on  blackboard  in  Laboratory.)  In  the  first 
wash  bottle  put  about  50  cubic  centimetres  of  water,  in  order  to 
absorb  any  hydrochloric  acid  gas  which  may  come  over  in  the  subse- 
quent procedure  ; in  the  second  put  the  same  amount  of  concentrated 
sulphuric  acid,  to  absorb  moisture  from  the  chlorine  gas,  which  is 
to  be  generated  later.  To  the  second  wash  bottle  attach  a piece  of 
hard  glass  tubing  about  50  centimetres  long  and  15  millimetres  in 
diameter  by  means  of  a glass  tube  and  cork.  The  other  end  of  the 
large  glass  tube  is  fitted  with  a cork  having  a small  glass  tube  about 
a foot  long  and  pointed  up  the  hood. 

Weigh  out  about  3 grams  of  aluminium  scrap,  wash  with  ether 
( beware  of  flame!)  to  remove  oil  and  dry  carefully  and  place  in  the 
end  of  the  hard  glass  tube  next  the  wash  bottles. 

Fill  the  flask  about  one  third  full  of  lumps  of  pyrolusite  (black 
oxide  of  manganese)  and  connect  up  the  apparatus,  making  sure  that 
all  the  joints  are  perfectly  tight.  Add  pure  concentrated  hydrochloric 
acid  enough  to  cover  the  pyrolusite  and  warm  gently  with  the  smoky 
flame  so  that  chlorine  is  evolved.  Pass  the  chlorine  through  the 
apparatus  until  all  the  air  is  driven  out,  and  then  with  a Bunsen 
burner  heat  the  aluminium  scrap.  This  soon  becomes  red  hot  and 
an  active  reaction  takes  place,  while  the  aluminic  chloride  formed 
sublimes  over  in  the  cool  end  of  the  tube  and  collects  as  a yellow 
solid.  The  heating  with  the  Bunsen  burner  is  continued  until  all  the 
aluminium  is  used  up  and  a small  black  mass  remains  ; then  the  burner 
is  taken  away  and  the  tube  allowed  to  cool,  but  the  stream  of  chlorine 
is  kept  passing  through  until  the  tube  is  cold  enough  to  be  grasped 
by  the  hand.  Stop  the  stream  of  gas  by  filling  up  the  gas  flask  with 


6 


water  and  disconnecting  from  the  wash  bottles.  (Save  this  liquor 
for  a future  experiment.)  Disconnect  also  the  hard  glass  tube  con- 
taining the  sublimate  of  aluminic  chloride.  Transfer  the  A1C13  to  a 
weighed  dry  bottle  as  hurriedly  as  possible,  and  weigh.  Calculate 
the  per  cent  of  yield  of  A1C13  from  the  known  amount  of  Al. 

As  aluminic  chloride  is  very  deliquescent,  in  handling  it  moisture 
must  be  avoided  as  much  as  possible.  This  salt  decomposes  some- 
what on  standing  and  gaseous  HC1  is  set  free;  therefore  be  very 
careful  about  opening  a bottle  of  this  substance,  especially  after  it 
has  been  standing  for  several  days. 

Throw  a small  lump  of  A1C13  into  a beaker  of  water;  test  the 
solution  with  litmus  paper. 

Prepare  Al  Cl3  in  the  wet  way.  How  can  you  do  this  ? Compare 
it  with  A1C13  prepared  by  the  dry  method. 


INORGANIC  PREPARATION  IX. 

Potassic  Dichromate  K2Cr207. 

(j From  Chrome  Iron  Ore.) 

Dissolve  56  grams  of  pure  K2C03  in  60  grams  of  water,  add  175 
grams  of  lime,  and  let  the  mixture  stand  till  the  lime  has  slaked. 
Evaporate  to  dryness  on  the  water  bath,  then  heat  gently  over  the 
free  flame  with  constant  stirring  until  the  mass  has  become  a dry 
powder.  Add  112  grams  of  powdered  chromite  (chrome  iron  ore, 
FeCr204)  and  mix  thoroughly.  Transfer  to  a clay  crucible  without 
cover  and  heat  to  a red  heat  with  the  oxidizing  flame  for  about 
3 hours  — stirring  occasionally. 

When  the  ignition  is  over  and  the  mass  is  cold  break  up  into  small 
lumps  and  extract  with  300  to  400  cubic  centimetres  of  water.  Filter, 
and  concentrate  the  filtrate  until  crystals  begin  to  appear,  at  which 
point  add  a concentrated  solution  of  20  grams  of  K2  S04  and  filter. 
To  the  yellow  filtrate  add  dilute  sulphuric  acid  till  strongly  acid,  and 
allow  the  solution  to  cool.  (Make  this  dilute  acid  by  adding  slowly 
1 volume  of  cone.  H2S04  to  2 volumes  of  water  contained  in  a flask. 
During  the  addition  of  the  acid  to  the  water,  shake  the  flask  and  cool 
under  the  water  tap.)  The  K2Cr207  will  precipitate  partly  on  the 
addition  of  the  acid,  and  more  on  cooling.  When  cold,  filter,  using 
an  asbestos  filter  and  the  Buchner  funnel.  Recrystallize  the  precipi- 


7 


tate  by  dissolving  it  in  the  smallest  possible  amount  of  hot  water, 
and  allowing  it  to  cool  slowly.  Filter  without  crushing  the  .crystals 
and  dry  in  the  drying  oven.  The  first  mother  liquor  contains  more 
of  the  dichromate  but  it  is  so  mixed  with  potassic  sulphate  that  the 
separation  of  the  two  is  not  practical. 

Reactions : The  ignition  of  the  potassic  carbonate,  lime,  and  chro- 
mite mixture  forms  potassic  chromate,  calcic  chromate,  and  iron 
oxide,  the  oxygen  necessary  coming  from  the  air.  The  excess  of 
lime  is  to  keep  the  mass  porous.  Any  impurity  of  sand  in  the 
chromite  forms  a slag  with  the  K2C03.  Reactions  : — 

2 FeCr204  + 4 K2C03  + 70  = 4 K2Cr04  + Fe203  + 4 C02. 

2 Fe Cr2 04  + 4 CaO  + 70  = 4 CaCr04  + Fe203. 

On  treatment  of  the  fused  mass  with  water  the  chromates  go  into 
solution,  leaving  the  iron  oxide  undissolved.  The  potassic  sulphate 
decomposes  the  calcic  chromate. 

CaCr04  + K2S04  = K2Cr04  + CaS04. 

The  sulphuric  acid  changes  the  potassic  chromate  into  potassic 
dichromate.  Write  the  reaction. 


INORGANIC  PREPARATION  X. 

Chromic  Oxide  Cr203. 

Please  perform  this  experiment  under  the  hood. 

12.5  grams  of  sodium  dichromate,  Na2Cr207,  are  moistened  with 
10  drops  of  water,  and  2 cubic  centimeters  of  glycerine  are  added, 
the  mixture  being  in  a copper  crucible  of  500 , cubic  centimeters 
capacity.  Stir  thoroughly,  warm  on  the  water  bath,  and,  as  soon 
as  the  mass  takes  fire , cover  the  crucible  with  an  earthenware  plate. 
(If  the  mixture  does  not  take  fire  of  itself  after  a few  moments,  set 
it  off  with  a lighted  match  held  in  a pair  of  tongs.) 

When  the  reaction  is  complete  and  the  vessel  is  cold,  the  resulting 
green  chromic  oxide  is  washed,  first  with  cold,  then  with  hot  water, 
and  filtered  from  all  soluble  material  by  means  of  a plaited  filter. 
Dry  the  Cr203  on  the  water  bath  and  ignite  a few  moments  in  a 
porcelain  crucible  with  the  Bunsen  lamp.  The  yield  should  be  about 
5 grams. 


8 


The  reactions  taking  place  between  Na2Cr207  and  glycerine  C3H803 
are  very  complex.  Two  of  the  products  are  Cr203  and  Na2C03,  and 
these  will  form  the  major  part  of  the  mixture  in  the  crucible  after 
the  combustion  is  over.  The  treatment  with  water  removes  the 
Na2C03  and  also  any  unchanged  Na2Cr207.  The  final  ignition  of 
the  Cr203  in  the  porcelain  crucible  is  to  destroy  any  last  traces  of 
organic  matter. 

Try  the  solubility  of  a small  amount  of  Cr203  in  water,  dilute 
HC1  and  NaOH. 


INORGANIC  PREPARATION  XI. 

Chromic  Chloride  CrCl3. 

.»*  4 • 

( Anhydrous .) 

Dry  chromic  chloride,  like  aluminic  chloride,  cannot  be  prepared 
pure  in  the  wet  wa}T,  so  the  following  method  is  used : — 

Set  up  an  apparatus  exactly  like  that  used  in  the  preparation  of 
aluminic  chloride  (Inorganic  Preparation  VII),  consisting  of  chlorine 
generator ; two  wash  bottles,  one  containing  water,  the  other  con- 
centrated sulphuric  acid;  and  the  hard  glass  tube.  In  the  hard 
glass  tube  at  the  end  nearest  the  second  wash  bottle,  place  a mixture 
of  5 grams  of  Cr203  and  1.2  grams  of  charcoal.  Pass  chlorine  gas 
slowly  through  the  apparatus  and  bring  the  end  of  the  hard  glass 
tube  containing  the  oxide-charcoal  mixture  to  a full  red  heat.  The 
chromic  chloride  sublimes  in  the  cool  end  of  the  tube  in  shining 
violet  leaflets.  When  the  reaction  is  complete,  allow  the  tube  to 
cool.  When  cold  stop  the  current  of  chlorine,  disjoint  the  hard 
glass  tube,  and  transfer  the  CrCl3  to  a dry  weighed  bottle.  Calcu- 
late the  per  pent,  yield  of  CrCl3  from  the  weight  of  Cr203  taken  at 
the  beginning  of  the  experiment. 

HegctLon : This  is  called  a concurrent  reaction.  The  formation  of 
the  CrClg  is  brought  about  by  the  combined  action  of  the  C and  Cl2 
on  the  Cr203. 

Cr203  + 3 C + 3 Cl2  = 2 CrCl3  + 3 CO- 

Try  the  solubility  of  CrCl3  in  pure  water  and  in  water  containing 
a small  amount  of  CrCl3  prepared  by  the  wet  method. 

Save  the  liquor  in  the  chlorine  generator  for  the  next  preparation. 


9 


' INORGANIC  PREPARATION  XII. 

Manganous  Chloride  Mn  Cl2 . 4 H20. 

The  source  of  the  manganous  chloride  is  the  waste  acid  liquor 
from  the  preparation  of  chlorine. 

Mn02  + 4 HC1  = Mn  Cl2  + 2 H20  + Cl2. 

Evaporate  the  liquor  to  dryness  on  the  steam  bath  in  order  to 
drive  off  the  excess  of  acid.  Add  a volume  of  water  equal  to  that 
of  the  liquor  used,  boil  about  ten  minutes,  and  filter  with  a plaited 
filter. 

Measure  out  one  tenth  of  the  filtrate  and  to  it  add  sodium  carbonate 
solution  to  complete  precipitation  of  the  manganese  as  carbonate 
and  of  the  impurity  of  iron  as  hydrate.  Wash  several  times  by 
decantation,  then  put  this  precipitate  into  the  main  portion  of  the 
above  mentioned  filtrate  and  boil  gently  for  half  an  hour,  or  until  a 
small  test  portion  treated  with  ammonium  sulphide  gives  a flesh 
colored  precipitate  which  is  soluble  in  dilute  acetic  acid.  Filter  and 
evaporate  to  the  point  of  crystallization.  The  crystals  of  manganous 
chloride  contain  4 molecules  of  water  — MnCl2  • 4 H20  — and  are 
deliquescent. 

In  the  purification  of  this  substance,  the  fcldition  of  MnC03  to 
the  solution  throws  down  the  impurity  of  iron  as  hydrate,  while  a 
corresponding  quantity  of  MnCl2  goes  into  solution.  The  amount 
of  iron  salt  is  usually  so  small  that  one  tenth  of  the  total  amount  of 
manganese  will  give  MnC03  enough  for  the  purpose.  Complete  and 
balance  the  reaction  : — 

MnC03  + FeCl3  -f  H20  == 

Divide  a solution  of  a crystal  of  MnCl2  in  a test  tube  into  two 
parts:  To  the  first  add  a few  drops  of  (NH4)2S;  to  the  second  a 
few  drops  of  a solution  of  Na2C03. 

INORGANIC  PREPARATION  XIII. 

^ Potassic  Permanganate  K\Mn04. 

Dissolve  35  grams  potassic  hydroxide,  in  50  grams  of  water  in 
an  evaporating  dish,  add  l&Lgrams  potassic 'chlorate,  and  heat  till 

completely  dissolved.  Add  to  this  solution,  with  stirring,  30  grams 

* 

ssr 


10 


of  pyrolusite  which  has  previously  been  ignited  on  an  iron  plate  to 
burn  out  organic  matter,  and  evaporate  to  a thick  paste.  This  paste 
is  now  transferred  to  a loosely  covered  iron  crucible,  dried  slowly, 
and  heated  to  redness  over  the  free  flame.  The  paste  turns  to  a 
dark  green  or  brown  solid  mass  and  water  vapor  escapes.  When 
quite  hard,  let  cool,  remove  the  mass  with  an  old  file,  and  pulverize 
it.  Boil  up  with  <500  cubic  centimeters  of  water  and  pass  a stream 
of  carbon  dioxide  into  the  hot  solution  for  three-quarters  of  an  hour. 
The  color  of  thfe  solution  changes  from  green  to  violet  and  a brown 
precipitate  is  thrown  down.  The  excess  of  potassic  hydrate  is  con- 
verted into  potassic  carbonate.  Allow  the  liquid  to  stand  a little 
while ; then  decant  the  supernatant  liquid  through  an  asbestos  filter, 
with  Buchner  funnel finally,  filter  off  the  precipitate,  and  evaporate 
the  filtrate  rapidly  over  the  free  flame  in  an  evaporating  dish  till 
crystals  begin  to  appear ; then  let  cool,  filter  with  suction,  and  dry 
in  a dessicator  over  sulphuric  acid.  Evaporate  the  filtrate  for  an- 
other crop  of  crystals. 

At  all  times  during  the  process  be  very  careful  to  keep  organic 
matter  out  of  the  reaction  mixture. 

Reactions : — 

6 Mn02  + 2 KC103  + 12  KOH=  6 K2Mn04  + 2 KCl+'6  H20. 
3 K2Mn04  + 6 H20  H 2 K Mn 04  + 4 KOH  -f  Mn02  + 4 H20. 

Experiment : — 

(a)  Dissolve  a crystal  of  KMn04  in  a quarter  of  a test  tube  of 
tap  water  and  boil.  What  occurs  ? (Tap  water  contains  organic 
matter.) 

( b ) Dissolve  a crystal  of  KMn04  in  a quarter  of  a test  tube  of 
water,  add  10  drops  of  dilute  H2S04,  and  pour  into  FeS04  solution. 
What  happens  ? 


INORGANIC  PREPARATION  XIV. 

\ 

Nickel  Nitrate  Ni(N03)2  • 6 H20. 

In  an  evaporating  dish  under  the  hood  place  20  grams  of  metallic 
nickel  and  add  concentrated  nitric  acid,  a few  cubic  centimeters  at  a 
time,  until  the  solution  of  the  metal  is  complete.  Avoid  much  of  an 
excess  of  acid  and  when  the  chemical  action  slows  down,  heat  the 
dish  with  the  Bunsen  flame.  When  the  metal  has  dissolved,  add 


11 


two  volumes  of  water  and  pass  H2S  into  tfye  solution  until  no  more 
precipitate  forms.  (This  throws  down  the  ipLphides  of  the  im- 
purities of  copper,  arsenic,  lead,  bismuth,  4*0  Filter  and  evapo- 
rate to  crystallization,  remembering  that;  slowlfcqoling  is  necessary 
for  the  formation  of  large  crystals.  Dry  thWrystals  in  a dessicator 
over  concentrated  sulphuric  acid. 

In  a dry  test-tube  heat  a crystal  of  nickel  ifitrate. 

INORGANIC  PREPARATION  XV. 

^ Mercuric  Oxide  HgO. 

In  an  evaporating  dish  under  the  hood  put  15  grams  of  mercury, 
and  treat  with  strong  nitric  acid  in  small  portions  until  the  metal  is 
entirely  dissolved.  Pour  the  solution  into  a beaker  and  add  a strong 
solution  of  potassic  hydrate  (made  by  dissolving  one  part  of  KOH 
sticks  in  four  parts  of  water)  to  complete  precipitation.  The  yellow 
precipitate  of  HgO  is  allowed  to  settle;  then  is  washed  four  times 
with  wrater  by  decantation.  Filter  on  cloth  and  transfer  to  a crystal- 
lizing dish  and  heat  in  the  air  bath  to  300°  for  one  hour.  Do  this 
under  the  hood , and  call  the  attention  of  the  instructor  to  the  appara- 
tus before  beginning  the  heating.  The  heating  changes  the  yellow 
modification  of  HgO  into  the  red. 

Heat  a small  quantity  of  HgO  in  a test  tube  with  the  free  flame. 

Complete  the  reactions  : — 

Hg  + HN  03  = 

Hg  (N 03)2  + KOH  = 

INORGANIC  PREPARATION  XVI. 

Phosphorus  Trichloride  PCl3. 

( Graebe , Chemisches  Central-blatt , ^2-926.) 

Consult  the  instructor  before  performing  this  experiment,  and 
show  him  the  apparatus  before  putting  in  the  PC13. 

Phosphorus  trichoride,  PC13,  is  a colorless  liquid  boiling  at  74°. 
It  fumes  in  moist  air  and  is  decomposed  by  water  and  many  organic 
substances.  Always  work  with  it  under  the  hood  and  avoid  inhaling 
the  vapors  from  it. 

To  prepare  PC13  set  up  the  following  apparatus.  (A  diagram 
will  be  found  on  the  blackboard.) 


12 


A chlorine  generator  and  two  wash  bottles,  such  as  were  used  in 
the  A1C13  and  CrCL  experiments,  are  connected  to  a glass  tube 
which  leads  to  the  bottom  of  a 500  cubic  centimeter  flask,  which 
flask  also  is  fitted  jjvith  a return  condenser  (Liebig  style).  In  the 
flask  place  10  grams  of  Ted  phosphorus  and  cover  it  with  a layer  of 
10  grams  of  PC13  "obtained  from  the  store-room.  Now  pass  a mod- 
erately rapid  stream  or-jchlorine  into  the  flask  until  the  phosphorus 
has  nearly  disappeared™  but  be  sure  it  is  not  all  used  up.  Stop  the 
stream  of  chlorine,  disconnect  the  apparatus,  attach  the  flask  to  a 
downward  condenser  (see  diagram  on  blackboard),  and  distil  the 
PC13  into  a dry  weighed  flask.  Calculate  the  per  cent,  yield  of 
PCI3  from  the  given  weight  of  red  phosphorus. 

Reaction : P + Cl2  = 

Perform  the  following  experiments  under  the  hood  : — 

Add  a drop  of  PC13  to  a beaker  containing  ten  cubic  centi- 
meters of  water  and  test  the  solution  with  litmus  paper  and  with 
AgN03  + HNO3  dilute.  Put  a drop  of  PC13  on  a watch-glass 
under  the  hood  and  blow  your  breath  over  it. 


INORGANIC  PREPARATION  XVII. 

Crystallized  Silicon  Si, 

Mix  thoroughly  10  grams  of  magnesium  powder  with  40  grams  of 
perfectly  dry  sand  and  transfer  to  a test  tube.  Put  the  test  tube 
into  an  iron  jacket  and  heat  with  the  Bunsen  flame,  moving  the 
latter  continuously  along  the  iron  so  that  the  whole  tube  is  equally 
heated.  Do  this  under  the  hood,  and  have  the  tube  supported  by 
an  iron  clamp  and  pointed  towards  the  hood  wall.  When  the  action 
is  over  let  cool,  and  break  the  test  tube  and  throw  into  a beaker  of 
dilute  hydrochloric  acid.  (This  is  to  get  rid  of  the  inflammable 
magnesium  silicide.)  Pulverize  the  product  and  filter.  Dry  the 
residue  thoroughly,  mix  with  10  times  its  weight  of  zinc,  and  heat 
to  fusion  for  several  minutes  in  a Hessian  crucible  in  the  furnace. 
Cool.  Wash  off  the  surface  of  the  zinc  with  water  and  then  dissolve 
it  in  dilute  hydrochloric  acid,  under  the  hood,  whereby  the  silicon  is 
left  undissolved  in  the  form  of  glistening  black  crystals.  Wash 
with  water,  dry,  and  bottle. 

■ Reaction:  Si02  + Mg  = 


13 


Sis  tie,  and  a layer  of 
surface.  Cover  the 


% and  very  quickly 
Jagnesium  powder, 


II. 


i>. 


[ss  ” in  a large 
Ilowed  to  cool. 


crucible  immediately  with  alight  fittimfrfon  plate.  Borax  contains 
usually  10  molecules  of  water.  Na2B407  • 10  H20.  The  dehy- 
drated salt  is  very  deliquescent,  and  therefore,  when  working  with 
it,  proceed  as  rapidly  as  possible  and  use  warmed  vessels. 

Place  the  crucible  in  the  furnace  and  heat  to  a red  heat  for  15 
minutes.  Cool;  pulverize  the  product  and  boil  with  water;  then 
with  dilute  hydrochloric  acid ; then  with  water  again  (decanting  off 
the  liquor  each  time),  and  filter.  This  gives  amorphous  — rather 
impure  — boron. 

To  obtain  the  pure  crystalline  variety,  mix  the  amorphous  boron 
with  five  parts  of  aluminium  scrap  in  a small  covered  crucible  and 
melt  in  the  furnace.  Let  cool,  dissolve  the  aluminium  with  dilute 
nitric  acid,  and  the  boron  crystals  will  be  left  behind  in  the  form  of 
quadratic  prisms  (boron  diamond).  Try  to  scratch  glass  with  one 
of  these. 


INORGANIC  PREPARATION  XIX. 


Boric  Acid  H3B03. 


Dissolve  100  grams  of  powdered  borax  in  300  cubic  centimeters  of 
nearly  boiling  water  and  concentrated  HC1  to  strong  acid  reaction. 
Allow  to  stand  till  perfectly  cold.  Filter  the  crystals  on  the  Buchner 
funnel  and  wash  with  a very  small  amount  of  water.  Redissolve 
the  crystals  in  the  smallest  possible  amount  of  hot  water  and  let  cool 
slowly.  Filter  with  the  Buchner  funnel  and  dry  a day  or  so  between 
sheets  of  filter  paper. 

Complete  the  reaction : Na2B407  + HC1  + H20  = 


14 


PREPARATION  XX. 

. 7 H20. 


Make  a cone 
hot  water,  and 
(keeping  it  hot 
mix  thoroughly  a: 
out  in  large  cryst 
quickly  between  sheets 
Place  the  rest  of  the  crys 


ms  of  sodium  carbonate  in 
Arts.  Saturate  one  part 
hen  add  the  second  part, 
odium  sulphite  crystallizes 
or  three  large  crystals ; dry 
ier  paper  and  preserve  in  a dry  bottle, 
back  into  the  filtrate  and  use  in  the 


preparation  of  sodium  thiosulphate. 
Reactions : — 


Na2COs  + 2 S02  + H20  = 2 NaHS03  + C02. 

2 NaHS03  + Na2C03  = 2 Na2S03  + 2 II20  + C02. 

This  salt  is  very  soluble  in  cold  water.  Try  a drop  of  the  solution 
with  a piece  of  turmeric  paper.  Expose  a crystal  to  the  air  on  a 
watch  glass  and  note  the  effect. 


Preparation  of  Sulphur  Dioxide  S02. 

For  use  in  the  above  experiment  the  sulphur  dioxide  may  be  pre- 
pared as  follows : — 

Place  30  grams  of  charcoal  in  a liter  flask,  which  is  fitted  with  a 
2-hole  rubber  stopper ; through  one  hole  have  a funnel  tube  reaching 
nearly  to  the  bottom  of  the  flask;  through  the  other  hole  have  a 
delivery  tube  bent  at  right  angles  and  connected  to  a gas  wash  bottle 
containing  50  cubic  centimeters  of  water.  From  the  wash  bottle  a 
tube  conveys  the  gas  into  the  Na2C03  solution.  When  the  apparatus 
is  ready  pour,  in  small  portions  at  a time,  100  grams  of  concen- 
trated sulphuric  acid,  warming  the  flask  until  the  reaction  begins. 
When  the  Na2C03  solution  is  saturated  with  the  S02  gas,  disconnect 
the  delivery  tube  and  stop  the  evolution  of  gas  by  the  addition  of 
much  water.  Perform  this  experiment  under  the  hood. 

Complete  the  reaction  : C + H2S04  = S02  -f- 


15 


To  the  boiling 
vious  preparation 
small  quantities 
rather  slowly.  Filter 
thin  syrup,  and  allow  to 
large  crystals  containing 
are  efflorescent. 

Heat  a crystal  in  a test  tube  in  the  free  flame. 

Reaction  for  preparation : Na2S03  -f-  S ==  Na2S203 


in  the  pre- 
of  sulphur  in 
reaction  runs 
the  filtrate  to  a 
thiosulphate  forms 
crystallization  which 


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